It is known to produce an image by the so-called electrographic recording process. As disclosed in Blumenthal U.S. Pat. No. 3,611,419, the electrographic recording process is generally characterized by two basic steps. In the first step, a recording medium is provided and an electrostatic latent image is established on the recording medium by electrostatic recording heads connected to charging circuit means. In the second step, the electrostatic latent image is rendered visible by development of the charged areas on the recording medium. The Blumenthal patent is concerned with an electrographic imaging system and heads therefor. The recording medium of Blumenthal, generally indicated by the numeral 14 in FIG. 2 of that patent, is made of a dielectric layer 16 in contact with a conductive layer 18. The particular materials to be used for each layer, and the method for making the recording medium, are not given by Blumenthal.
In Tagawa U.S. Pat. No. 4,030,107, there is shown an electrographic recording device employing electrostatic induction electrodes. Here again, the patentee was primarily concerned with the electronics and the electrodes for use in an electrographic recording process: he was not particularly concerned with the recording medium therefor. In Tagawa, the recording medium 7 shown in FIG. 1 is made of two parts: a low resistance layer 7b and another layer 7a which appears to be not defined in the patent. In any event, the method of making the recording medium and the materials therefor are not stated in the Tagawa patent.
It is, therefore, an object of the present invention to provide a method for making a novel electrostatic recording medium;
It is another object of the present invention to provide a novel electrostatic recording medium for use in an electrographic process.
It is a further object of the present invention to provide a novel electrostatic recording medium whose volume resistivity is relatively unaffected by changes in humidity conditions.
These and other objects of the invention can be gathered from the following detailed disclosure.